Axoplasmic constituents of crayfish nerve cord are being studied using combined electron microscopic and biochemical approaches, with the emphasis on microtubules (MTs) and tubulin, the constituent protein of MTs. Nerve cords incubated for varying time periods in media containing radioactive precursor molecules will be prepared for EM autoradiography as well as SDS polyacrylamide gel electrophoresis, with the activity in the gel bands counted by liquid scintillation spectrometry. Also, studies will be completed dealing with the effect of temperature on protofilament number in MTs polymerized from crayfish nerve cord tublin, and preliminary studies are to be undertaken dealing with the nature and role of proteins associated with the surfaces of these and other MTs. In addition, early stages in the formation of MTs from tubulin will be examined and reconstructed. A search for actin in axons of crayfish nerve cord is being continued, and several diagnostic methods are being employed. In the case of the rickettsia, Coxiella burneti, studies are nearing completion on the cytopathic effects of short and long-term infections in mouse L and Vero cells, and the precise ultrastructural events of binary fission are being reconstructed. BIBLIOGRAPHIC REFERENCES: Lewis, J. C., and P. R. Burton, 1976. Ultrastructural studies of the superior cervical trunk of the mouse. I. Distribution of microtubules and neurofilaments in preganglionic fibers. J. Neurocytology. Lewis, J. C., and P. R. Burton, 1976. Ultrastructural studies of the superior cervical trunk of the mouse. II. Cytochemistry and stability of fibrous elements in the axoplasm. J. Neurocytology.